Portion of a display screen with a graphical user interface



FIG. 1 is a front view of a portion of a display screen with a graphical user interface; and,

FIG. 2 is a front view of a portion of a display screen with a graphical user interface.

The broken lines illustrating a portion of a display screen form no part of the claimed design. 

CLAIM The ornamental design for a portion of a display screen with a graphical user interface, as shown and described. 